Ejector mechanism for a plastic injection molding machine or the like



F'IG-| Dec. 31, 1968 H. H. COLLINS EJECTOR MECHANISM FOR A PLAST INJECTION MOLDING MACHINE THE KE Filed Aug.

mvsu'ron. HARVEY H. COLLINS g ATTORNEYS United States Patent Ofi ice Patented Dec. 31, 1968 3 418 684 EJECTOR MECHANI SM i OR A PLASTIC INJEC- TION MOLDING MACHINE OR THE LIKE Harvey H. Collins, North Wilbraham, Mass., assignor to Package Machinery Company, East Longmeadow,

Mass., a corporation of Massachusetts Filed Aug. 31, 1966, Ser. No. 576,395 3 Claims. (Cl. 18-2) This invention relates to improvements in a plastic injection molding machine or the like and, more particularly, to an improved ejector mechanism for such machines.

In machines such as plastic injection molding machines and die casting machines, there is a movable die member reciprocable relative to a fixed die member, the said members being closed or engaged to define the die or mold cavity in which a part is cast. The die members are usually so constructed that the movable member carries the cast or molded part away from the fixed die member when they are separated. A conventional mechanism for ejecting the part from the movable die member includes at least one and generally a plurality of ejector rods which are slidable through the movable die and its support plate. The rear ends of these rods are generally fastened to a common ejector plate which is spring-biased rearwardly of the die support plate and which will engage a wall or some other abutment just prior to the completion of the rearward movement of the die to thrust the ejector rods forwardly to eject the part.

This is known as bumper ejection and it has certain disadvantages. For example, the slamming and banging and the wear on the parts is undesirable, and it is necessary to provide new ejector rod apertures through the movable die support plate to accommodate a diflFerent die having a diflFerent die cavity for the making of a different part.

It is the general object of the present invention to provide a self contained automatically operable ejector mechanism which does not have to strike a Wall or otherwise depend upon bumper actuation with its disadvantages and which is readily adaptable for use with various dies without modification of the movable die support plate.

As will be described in greater detail hereinafter, the ejector mechanism includes a reversible fluid motor having a cylinder element and a piston element, one of which is secured to the rear of the die support plate. The other element has at least one rod connected thereto which is slidable through the die support plate, and an ejector plate is disposed forwardly of the die support for movement by the said rod. One or more ejector rods are connected to the ejector plate and slide through the die to the die cavity in the ejecting operation. Whenever a die is changed, it is only necessary to change the ejector plate and the ejector rods for the new die and die cavity.

The drawing shows preferred embodiments of the invention and such embodiments will be described, but it will be understood that various changes may be made from the constructions disclosed, and that the drawing and description are not to be construed as defining or limiting the scope of the invention, the claims forming a part of this specification being relied upon for that purpose.

Of the drawing:

FIG. 1 is a vertical cross-sectional view taken through the movable die area and its operating linkage in a plastic injection molding machine;

FIG. 2 is an elevational view taken from the rear and showing the ejector mechanism of this invention;

FIG. 3 is a wiring diagram providing a schematic illustration of an exemplary control for the ejector mechanism; and

FIG. 4 is a vertical cross-sectional view taken through the movable die area showing a modified form of ejector mechanism according to the present invention.

In FIG. 1 a portion of a plastic injection molding machine vis shown, and this includes a movable die half 10 and a fixed die half 12. When these die halves are engaged, they cooperate to define a die or mold cavity for the making of a plastic part by injection, and each die half defines a part of the cavity, the cavity section in the die half 10 being identified by the number 14, and the section in the die half 12 being identified by the number 16.

As more fully described in my copending U.S. application, Ser. No. 559,861, filed June 23, 1966, and entitled Operating Linkage for a Plastic Injection Molding Machine or the Like, such a machine includes a movable die support plate 18 and a fixed die support plate 20. A plurality of tie rods 22, 22 extend rearwardly from the fixed die support plate 20 to a rigid stock or base 24, and the movable die support plate 18 moves horizontally forwardly over the tie rods 22 to engage the movable die half 10 with the fixed die half 12 and the movable die support plate 18 is then retracted or drawn rearwardly toward the position shown in FIG. 1. In keeping with conventional practice, the die cavity section 14 in the movable die 10 is formed to retain the finished or cast part as the movable die is retracted so that the part is withdrawn from the machine by being ejected from the movable die half 10.

The mechanism for reciprocating the movable die support plate 18 and thus the movable die 10 includes the linkage structure indicated generally by the reference number 26, and this linkage is actuated by moving a crosshead 28 forwardly and rearwardly along a guide rod or beam 30 which moves with themovable die support plate 18 through an extension 32 on the stock 24 which is disposed rearwardly of the said stock as more fully described in my said copending application.

The ejector mechanism provided in accordance with the present invention is indicated generally by the reference number 34 and it is adapted to operate to eject a molded part from the movable die member or half 10 when the movable die support plate 18 is moved rearwardly to the fully retracted position shown in FIG. 1 or selectively to operate for ejection when the said plate has been withdrawn to an intermediate position. The said mechanism 34 includes a fluid motor (preferably an hydraulic motor) comprising a cylinder element 36 and a piston element 38. The said fluid motor is reversible, and to this end fluid conduits or hose connections 40, 40 are provided at each end of the cylinder 36 to accommodate reversible fluid flow therethrough. Either the said cylinder element or the said piston element is fixedly secured to the rear face of the movable die support plate 18 and the other element is reciprocable relative thereto.

In the preferred form shown in FIGS. 1 and 2, the piston element 38 is fixedly secured to the movable die support plate 18 as by screws 42, 42 so that the cylinder 36 can move forwardly toward and rearwardly from the movable die support plate. A cylinder plate 44 is connected as by screws 46, 46 to the front end of the cylinder element 36, and a plurality of rods 48, 48 are fastened to the cylinder plate to project forwardly therefrom and to slide through suitable openings provided in the movable die support plate 18.

The cylinder plate rods 48, 48 are operatively associated with an ejector plate 50 at their front ends. This ejector plate is movable forwardly and rearwardly within an opening 52 provided on the rear face of the movable die 10, and the ejector plate carries one or more ejector rods, such as the rod 54 which is movable slidably through an opening in the movable die 10 to project into the die cavity area 14 and thus to eject a molded part therefrom when the ejector plate 50 is thrust forwardly. The said ejector plate can be spring-biased rearwardly in the die opening 52 and thrust forwardly by engagement from the front ends of the cylinder plate rods 48, 48 to effect bumper ejection. However, in the preferred form, the cylinder plate rods 48, 48 are threaded in the rear surface of the ejector plate 50 adjacent the front surface of the die support plate 18 so that the said ejector plate will move forwardly and rearwardly in the die space 52 with forward and rearward movement of the cylinder 36.

In keeping with this invention, the ejector mechanism 34 is to be operated automatically whenever the movable die support plate 18, and thus the movable die 10, reaches a predetermined or preselected rearward position relative to the fixed die 12. This position of the movable die support plate 18 for operation of the ejector mechanism is determined when a limit switch LS-1 (FIG. 3) is engaged and closed. As explained in another of my copending applications, Ser. No. 572,010, filed Aug. 12, 1966, and entitled Control Switch Actuating Apparatus for a Plastic Injection Molding Machine or the like, the limit switch LS-l can be located on the machine frame for direct engagement and operation by the support plate 18, or it can be remotely located and actuated by means movable with the said die support plate.

There are a variety of control circuits that can be provided for automatic operation of the ejector mechanism 34, and that shown in FIG. 3 is merely exemplary. In the said exemplary arrangement, the limit switch LS-l is normally open and is arranged to be closed when the movable die support plate member 18 reaches the desired position for the start of the ejector cycle. The said limit switch is connected in series with a second normally open limit switch LS-2, a solenoid adapted to operate a control valve (not shown) for effecting forward movement of the cylinder 36, a time delay relay designated TDR-l, and the normally closed contacts of a second time delay relay TDR-2. Normally open contacts operated by the relay TDR-l bridge the limit switches LS-1 and LS-2 so that the forward operating solenoid will remain energized for the time delay period set in the relay TDR-1 which is sufiicient to complete the forward movement of the cylinder 36 and thus to complete the ejection. The limit switch LS-2, as shown in FIG. 2, is mounted on a bracket 60 carfied by the movable die support plate 18. This limit switch has an operating arm 62 arranged to be engaged and actuated by a cam 64 carried by the cylinder plate 44.

The said operating arm 62 is engaged and the limit switch LS-2 is closed by the cam 64 when the cylinder 36 is in its fully retracted or rearward position shown in FIG. 1. Thus, with the cylinder 36 retracted, when the movable die support plate 18 moves rearwardly to a position wherein the limit switch LS-l is closed, the forward solenoid is energized and the cylinder 36 moves forwardly to eject the part, and it will continue to move forwardly to the limit of its movement within the time permitted by the time delay relay TDR1.

At the completion of the forward or ejection stroke, a second cam 66, adjustably mounted on a bracket 68 secured to the first cam 64, will engage and actuate an operator 70 for a third limit switch LS-3 which is also mounted on the bracket 60 as shown in FIG. 2. As shown in FIG. 3, the limit switch LS-3 is normally open but it is actuated to close upon completion of the forward or ejector stroke, and it is connected in series with a reversing solenoid, the second time delay relay 'IDR-Z and the normally closed contacts TDR1 of the first-mentioned time delay relay. The time delay relay TDR-2 has normally open contacts which bridge the limit switch LS-3 and which will close to maintain the reversing solenoid energized for the timed period of the relay TDR-Z. The reversing solenoid operates to move the cylinder 36 rearwardly, and it is able to do this because the relay TDR-Z 62 to again close the limit switch LS-Z so that a repeated cycle of operation can take place whenever the limit switch LS-l is again closed.

In the alternative form of construction shown in FIG. 4, the piston or piston rod 38 is not connected to the movable die support plate 18 but instead has an extension 72 which slides through a suitable opening in the support plate to extend to the front surface thereof wherein it is connected to the ejector plate 50 as by one or more screws 74. Also in this modified or alternative form, the cylinder plate 44 has no rods extending through the die support plate and it is rigidly connected to the die support plate as by screws 76, 76. Thus, in the alternative form the piston reciprocates relative to the die support plate while the cylinder remains stationary. In this embodiment as in the first embodiment, the ejector plate 50 carries one or more ejector rods projecting through and slidable through suitable openings in the movable die half 10. Here again, the ejector plate 50 can be spring-biased rearwardly and merely engaged by the forward end of the piston rod extension 72 for bumper ejection, but preferably the ejector plate is connected to said extension for positive ejection operation.

In the alternative form of FIG. 4, wherein the cylinder plate 44 does not move, the limit switches LS-Z and LS-3 cannot be engaged and actuated by movement of the cylinder plate. An equivalent structure can be employed by having similar limit switches engaged and operated by suitable means carried by the ejector plate 50. In such arrangement, the limit switches are preferably supported on the movable die member 10, and the automatic control or operation will be the same.

The invention claimed is:

1. An ejector mechanism for a plastic injection molding machine or the like having a plate supporting a first die half for movement forwardly into engagement with a fixed second die half to define a cavity therewith and rearwardly to carry a part molded in the cavity away from the fixed die half, said mechanism comprising a reversible fluid motor including a cylinder element and a piston element, one of said elements being secured to the rear of said die support plate and the other element having at least one rod connected therewith and slidable through said die support plate, an ejector plate disposed forwardly of said die support plate for reciprocation relative to said first die half and movable forwardly by said rod, and at least one ejector rod secured to said ejector plate and slidable through said first die half to eject said molded part with forward movement of said other element, and wherein the piston element is secured to the rear of the die support plate, a cylinder plate is secured to said cylinder and has more than the said one rod secured thereto and slidable through said die support plate.

2. Ejector mechanism as defined in claim 1 including automatic means for controlling ejector operation, said control means comprising first and second electrical switches operable when said die support plate and said cylinder, respectively, are in predetermined rearward positions to cause said cylinder to move forwardly for ejection, and a third switch operable when said cylinder has moved forwardly to effect ejection to cause said cylinder to more rearwardly.

3. The ejector mechanism defined in claim 2 wherein said second and third switches are supported by said die,

References Cited UNITED STATES PATENTS Marsh. Caron. Strauss.

6 3,091,809 6/1963 Trueblood. 3,142,863 8/1964 Mazzoni. 3,357,058 12/ 1967 Kutik.

FOREIGN PATENTS 12,134 8/1962 Japan.

I. HOWARD FLINT, JR., Primary Examiner.

U.S. C1. X.R.

Beatty 249- 68 10 249-68 

1. AN EJECTOR MECHANISM FOR A PLASTIC INJECTION MOLDING MACHINE OR THE LIKE HAVING A PLATE SUPPORTING A FISRT DIE HALF FOR MOVEMENT FORWARDLY INTO ENGAGEMENT WITH A FIXED SECOND DIE HALF TO DEFINE A CAVITY THEREWITH AND REARWARDLY TO CARRY A PART MOLDED IN THE CAVITY AWAY FROM THE FIXED DIE HALF, SAID MECHANISM COMPRISING A REVERSIBLE FLUID MOTOR INCLUDING A CYLINDER ELEMENT AND A PISTON ELEMENT, ONE OF SAID ELEMENTS BEING SECURED TO THE REAR OF SAID DIE SUPPORT PLATE AND THE OTHER ELEMENT, HAVING AT LEAST ONE ROD CONNECTED THEREWITH AND SLIDABLE THROUGH SAID DIE SUPPORT PLATE, AN EJECTOR PLATE DISPOSED FORWARDLY OF SAID DIE SUPPORT PLATE FOR RECIPROCATION RELATIVE TO 